create over flow

I have simulated a bicycle helmet and want to create an over flow . The experimental set up uses a ventillater on a man riding a stationary bike. I want to simulate the heat transfer. My problem is how can I create inlet for the flow. Do you think it is advisable to model a big room and inlet somewhere in the room? Currentely I have only the helmet model.

If you want to look at the flow around the helmet and the heat transfer from the outside-in, then you need to model a domain around the helmet. So having a large box around it is a way to do it. What you want to ensure is that the flow can develop prior to reaching the helmet, and that any recirculation and turbulence effect has dissipated. So I think that one length scale btw the helmet and the inlet and 3 maybe behind it is advisable. This is how one would do for a car or a plane simulation.

Thanks Herve for your advice, but do you think it is avisable if I make the face of the box infront of the helmet back side of the helmet as open space i.e. by labelling the two opposite faces inlet and outlet?

I think you could (you could also use inlet and opening in CFX-5), but you want to make sure that the situation you model is as close as possible from your wind tunnel set up (e.g. is your helmet mounted on a kind of "human head"?). So watch out for the other boundary conditions and the other solids in the domain. If your helmet is symmetrical use a symmetry plane.

hello, I'm simulating the airflow over a bicycle helmet and i'm using different geometries for the simulations. Can you send me your helmet model? I'ill be waiting for your answer.
thank you

Quote:

Originally Posted by Tadiwos
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I have simulated a bicycle helmet and want to create an over flow . The experimental set up uses a ventillater on a man riding a stationary bike. I want to simulate the heat transfer. My problem is how can I create inlet for the flow. Do you think it is advisable to model a big room and inlet somewhere in the room? Currentely I have only the helmet model.